Size‐Dependent Dispersion of Rhodium Clusters into Isolated Single Atoms at Low Temperature and the Consequences for CO Oxidation Activity

Abstract

Understanding the dynamic structural evolution of supported metal clusters under reaction conditions is crucial to develop structure reactivity relations. Here, we followed the structure of different size Rh clusters supported on Al2O3 using in situ/operando spectroscopy and ex situ aberration‐corrected electron microscopy. We report a dynamic evolution of rhodium clusters into thermally stable isolated single atoms upon exposure to oxygen and during CO oxidation. Rh clusters partially disperse into single atoms at room temperature and the extent of dispersion increases as the Rh size decreases and as the reaction temperature increases. A strong correlation is found between the extent of dispersion and the CO oxidation kinetics. More importantly, dispersing Rh clusters into single atoms increases the activity at room temperature by more than two orders of magnitude due to the much lower activation energy on single atoms (40 vs. 130 kJ/mol). This work demonstrates that the structure and reactivity of small Rh clusters are very sensitive to the reaction environment.

Reactant-Induced Structural Evolution of Pt Catalysts Confined in Zeolite

“…In other cases, the exposure of metal particles to the reaction atmosphere will cause the redispersion of metal species and lead to improvements in catalytic performances. 11,12 In this regard, studying the structural evolution of metal species under reaction conditions is not only beneficial for in situ generation of highly active sites but also helpful in avoiding the undesired reactant-induced deactivation. 11−16 Previous studies have shown the dynamic structural evolution of metal catalysts on open-structure solid carriers (e.g., Al 2 O 3 , TiO 2 , and CeO 2 ) in different atmospheres and metal catalysts confined in zeolites in oxidation−reduction atmospheres.…”

“…However, the continuous sintering of Au clusters into Au nanoparticles leads to catalyst deactivation. In other cases, the exposure of metal particles to the reaction atmosphere will cause the redispersion of metal species and lead to improvements in catalytic performances. , In this regard, studying the structural evolution of metal species under reaction conditions is not only beneficial for in situ generation of highly active sites but also helpful in avoiding the undesired reactant-induced deactivation. − …”